Crozet Farm to Plant Chestnut Hybrids in Restoration Effort

By: Aaron Richardson (6 April 2012)

Chestnut planting

Above: A large-scale planting of chestnut seedlings is seen at a farm in Washington County, Va.

At the turn of the 20th century, it was nearly impossible to go outside in Central Virginia and not see a towering American chestnut tree. At that time, American chestnuts accounted for nearly one in four of the trees in the Blue Ridge Mountains.

Then, in barely half a century, the American chestnut was gone.

The hardy trees, prized for their rot-resistant hardwood lumber and plentiful nuts, had been killed by a fungal blight carried by the Chinese chestnut.

The American trees had no resistance to the fast-moving blight, which spread at a rate of 50 miles a year across the tree’s Maine-to-Georgia range.

Beginning today, Fried Farm in Crozet will join an effort to introduce a blight-resistant hybrid of the American chestnut and the Chinese chestnut to Central Virginia.

Owner Barbara Fried said the possibility of reviving the once-plentiful trees and a love of forests drew her to the project.

“It’s a magnificent tree and it’s as American as they come,” Fried said. “It would be exciting if the one that were the best hybrid were on our property.”

Fried said today’s planting won’t be the first time she has tried to grow American chestnuts.

“My husband and I always were interested in forests and trees, and earlier I had planted some trees and put wire around them and they just didn’t survive,” she said.

Volunteers with the American Chestnut Foundation will plant three acres of the farm with 169 germinated seeds of American-Chinese chestnut hybrids. The trees are the result of an ACF breeding program that crosses the blight-resistant Chinese chestnut with the vulnerable American tree.

The foundation wants to breed trees that contain as high a proportion of American chestnut genes as possible, but contain enough of the Chinese tree’s DNA to combat the blight.

According to Cathy Mayes, chairwoman of the ACF’s Virginia chapter, the Chinese chestnut was introduced to the United States by European immigrants who wanted a tree that would grow well in orchards and be easy to gather nuts from.

American chestnuts, she said, fare much better in forests, and, because of their size, are extremely difficult to harvest from.

Before the blight, Mayes said, the tree was a vital part of the economy and environment throughout its range. Chestnut trees fed and housed small mammals and birds, which became prey for larger animals. People harvested the trees for lumber, which was strong and easy to saw.

“At the time that the blight came through, chestnuts were as common as grass,” Mayes said. “So when the blight came through it was just devastating to the economy, the ecology and the beauty of the state.”

The fungus, Mayes said, took about 100 years to gain a foothold in the American chestnut population. After that, it spread quickly.

“Once it was diagnosed as a fungus, it wiped out about 4 billion trees in about 50 years,” she said. “Whole hillsides looked like toothpicks.”

The blight, which entered the tree through a wound in the bark, generally killed infected trees within a year of infection.

The trees going in at Fried Farm are fourth-generation hybrids, which contain 93 percent American genes. Genes from the Chinese trees give the hybrids a moderate resistance to the blight. When these trees reach sexual maturity, in about 10 years, they will be bred together in the hopes of finding a small number of strongly blight-resistant trees.

Virginia ACF President John Scrivani, who spent 20 years with the Virginia Department of Forestry, said the process of breeding blight-resistant trees will not be a quick or easy process.

“Our restoration plan is very long-term,” Scrivani said. “It will take hundreds of years to get the population re-established in the forest anything like what it was 100 years ago.”

Creating the hybrids that will go on Fried Farm takes breeding a Chinese chestnut and an American chestnut, then breeding the hybrid offspring with full American chestnuts, a process called backcrossing.

The trees planted at Fried will be bred together, which should produce one in 64 offspring that contain the strong resistance gene. When a strong population of those trees exists, they will be bred to reliably produce strongly blight-resistant trees.

“You can expect that if you perfectly picked resistant trees, that they will all be resistant,” Scrivani said. “There will be errors, but we’re pretty confident we can generate a population that will be strongly resistant.”

Similar orchards of blight-resistant trees already exist in Washington County, but planting those trees in this part of the state would limit genetic diversity.

To keep the population diverse, Scrivani said, trees must be bred in the general area they will repopulate. That allows the trees to adapt to the soils and climate of different parts of their range, which gives them a much better chance of survival.

“The [trees] that are being planted [today] are Central Virginia trees,” Scrivani said. “In 10 to 15 years, we’ll be able to plant these out to create that [resistant] generation for Central Virginia.”

While the native American chestnut population was devastated by the blight, some trees still get big enough to flower, which means they can breed. Their genes are harvested to help create a blight-resistant population of trees native to this area.

“We do find the rare surviving tree that has grown large enough to flower, and that is how we get local genetics into the population,” Scrivani said.

Planting the trees is an all-volunteer activity. The planting kicks off at 9:30 this morning, and Fried said she has plenty of extra trowels for those who want to help.

“The chestnut foundation is comprised of a lot of good volunteers,” Fried said. “They couldn’t get by without the help of their volunteers.”


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